Mycobacterium tuberculosis the causative agent of Tuberculosis (TB) is the leading cause of infectious disease mortality in the world by a bacterial pathogen. A primary feature of this slow-growing organism that makes it difficult to treat is the thick waxy cell wall that provides an intrinsic barrier to many drugs. The mycolic acids represent one of the central components of the mycobacterial cell envelope and are essential for survival. The first-line drug isoniazid inhibits the enzyme known as InhA involved in early stages of mycolic acid biosynthesis; however, resistance to this agent has prompted research into other potential enzyme targets involved in mycolic acid synthesis. Recently, a monomodular polyketide synthase known as pks 13 was identified that performs the final biosynthetic operation leading to mycolic acids. Polyketide synthases are multifunctional enzymes and have been intensively investigated in the last decade for their involvement in the synthesis of bioactive natural products, a field termed combinatorial biosynthesis. The findings that PKSs are involved in the synthesis of the mycolic acids uncover a more sinister role for these fascinating enzymes. Rationally designed small-molecule inhibitors targeting one of the crucial domains of Pks13 will be synthesized. These will be assayed for in vitro activity using a cell-free enzyme assay. Structure-based and ligand-based computational methods will be employed to provide insight into the observed activity data. Active compounds will be further evaluated against whole-cell M. tuberculosis. A combination of lipid analysis and microarray profiling will be performed to verify the proposed mechanism of action. This proposed research is expected to validate Pks13 as a drug target and may lead to a new class of antitubercular compounds that target the penultimate step of mycolic acid biosynthesis. Additionally, this strategy may be adapted to inhibit critical PKSs from other pathogenic microorganisms. [unreadable] [unreadable] [unreadable]